The present invention relates to a drive circuit used for inverters or the like that drive an illumination unit such as a cold cathode fluorescent lamp or an EL display (electroluminescence display) and the like.
Heretofore, a ballastless type discharge lamp drive circuit using a multilamp leakage transformer as a circuit for driving a plurality of discharge lamps has been known (for example, refer to official gazette of Japan Tokkai 2002-075756). Furthermore, a discharge lamp drive circuit has been developed which drives by connecting primary sides of a plurality of output transformers in parallel and connecting the discharge lamps to the secondary sides of each output transformer.
Furthermore, heretofore, in case where an illumination unit, such as a plurality of cold cathode fluorescent lamps, is driven by using a high tension terminal at a secondary side of the wound transformer of one input and two outputs, as shown in FIG. 17, primary sides of each transformer T1, T2, T3 are connected in parallel, and the illumination units L1–L6 are connected independently to each transformer T1, T2, T3, as shown in the drawing.
In case where the primary sides of a plurality of output transformers are connected in parallel, and the lamps, such as the cold cathode fluorescent lamps, are driven for each output transformer, dispersion occurs in characteristics of the output transformer or the load even if they are of the same standard, and dispersion occurs in brightness of the lamps connected to each output transformer due to the foregoing dispersion.
An object of the present invention is to solve the foregoing problems.
Furthermore, in case of driving a plurality of the lamps, a system of connecting the electrode of the one lamp to the high tension terminal at the secondary side of the output transformer and driving the lamp by connecting the other electrode to the earth is generally employed. This system, however, has drawbacks such as causing a potential difference at both terminals of the lamp due to the one terminal side of the lamp being earthed that results in lower voltage of one terminal side of the lamp, and the high tension terminal connection side of the output transformer becomes bright, and the earth side becomes darker, and furthermore, dispersion occurs in luminance between the lamps.
Another object of the present invention is to solve the foregoing problems.